1. Field of the Invention
The present invention relates to a grinding sludge compacting machine for compressing a grinding sludge of hardened component parts produced in a grinding line, for example, a grinding sludge of ferrous component parts such as inner and outer races and rolling elements and others of rolling bearings and other bearing steel material, to thereby provide a briquette.
2. Description of the Related Art
Ferrous component parts of rolling bearings such as inner and outer races and rolling elements are, after having been hardened, subjected to a grinding process to grind raceways and others. Powdery grinding scraps produced as a result of the grinding are discharged as a sludge together with a coolant to the outside of the system and are then filtered so that the coolant can be reused. The grinding sludge left as a result of the filtration is in most cases buried in landfill.
However, not only is the use of the grinding sludge for landfill generally considered undesirable from the standpoint of environmental pollution, but also it is obvious that in view of the waste treatment sites reaching an dead end, the grinding sludge would no longer be used for land reclamation. Although the amount of the grinding scraps produced as a result of the grinding is relatively small as compared with the amount of cutting scraps, a mass-production line for manufacture of, for example, bearings results in a relatively large quantity of the grinding scraps
For this reason, it has been suggested to compress the grinding sludge by squeezing to provide a compressed material (referred hereinafter to as a “briquette”) so that the coolant squeezed therefrom can be reused while the briquette can be used as a material for steel production.
While the grinding sludge using an aqueous coolant can easily be compressed to provide the briquette, an oil-based coolant has a higher viscosity than that of the aqueous coolant and, therefore, the grinding sludge using the oil-based coolant poses various problems in compressing it. By way of example, during squeezing the oil-based coolant is difficult to be drained and even though the pressure used during squeezing is increased, compression of the grinding sludge to a required strength cannot be achieved. For this reason, compression of the grinding sludge containing the oil-based coolant has not yet been practiced.
Compression of the grinding sludge is considerably affected by the viscosity of the coolant being squeezed during the compressing process. Not only where the coolant is oil-based, but also where it is water-based, it tends to be considerably affected by the coolant viscosity. In particular, at the time of the start-up in the morning during the winter season, the grinding sludge compacting machine and the grinding sludge are both cold with the coolant consequently exhibiting a high viscosity enough to make it difficult for the coolant to be discharged through a gap. Accordingly, when attempt is made to forcibly apply a pressure to the grinding sludge to compress the latter, the coolant and the grinding scraps are mixed to form a sludge which subsequently flow out, making it difficult for the grinding sludge to be satisfactorily compressed.
As a machine for compressing a grinding sludge containing an oil-based coolant, the applicant(s) of the present invention has suggested a machine in which the pressure used for squeezing is controlled to a predetermined value and a predetermined compressing speed such as described in the Japanese Laid-open Patent Publication No. 2001-315000. According to this prior invention, the grinding sludge containing the oil-based coolant of a high viscosity can be satisfactorily compressed. However, it cannot accommodate change in parameter that affects the squeezing and, in the event that the parameter such as, for example, the ambient temperature or the oil content in the grinding sludge that affects the squeezing changes, it may be suspected that no satisfactory squeezing to provide the briquette can be achieved.
In general, because the grinding sludge contains so large a quantity of the coolant that the grinding sludge cannot be squeezed directly, the grinding sludge containing the coolant is, prior to being squeezed, filtered to provide a concentrated sludge which is subsequently compressed by the grinding sludge compacting machine to provide a briquette.
The grinding sludge compacting machine for compressing the grinding sludge has hitherto been available in the following two types; a gate type and a plug-like double cylinder type.
The gate type grinding sludge compacting machine includes, as shown in FIG. 9, a cylindrical mold 81 for accommodating a grinding sludge therein, a gate 82 for closing one end of the cylindrical mold 81 and a pressure applying piston 83 reciprocatingly movably inserted in the cylindrical mold 81 from the opposite end thereof. By pressing the piston 83 by means of a pressure applying cylinder 85, the grinding sludge can be squeezed within the cylindrical mold 81 to provide a briquette B.
The grinding sludge compacting machine of the plug-like double cylinder type includes, as shown in FIG. 10, a cylindrical mold 91 and first and second pressure applying pistons 92 and 93 reciprocatingly movably inserted in the cylindrical mold 91 through opposite ends thereof, respectively. The first and second pistons 92 and 93 are pressure applying sub-piston and main piston, respectively, which are driven by a sub-cylinder 94 and a main cylinder 95, respectively. The sub-piston 92 is held at a fixed position during the squeezing process and is adapted to be retracted away from the cylindrical mold 91 when the resultant briquette B is to be ejected out of the cylindrical mold 91.
The foregoing two systems have their own problems which will now be discussed.
(1) Gate Type (FIG. 9)
Since the sliding gate 82 is almost unable of being sealed against the cylindrical mold 81, it works while the grinding sludge is intruded into a gap therebetween and, for this reason, frictional wear is apt to occur. Once rattling occurs because of it, the gap increases and, once this gap increases to a size exceeding a limit, either the grinding sludge will blow off during the compressing operation, or the sludge will solidify within the gap between the gate 82 and the end face of the sleeve 81 with the coolant being consequently unable to be drained, resulting in difficulty in accomplishing the compression of the grinding sludge. Also, since the gate selectively open or close while the briquette B is purged firmly against the gate 82, frictional wear of respective contact surfaces of the gate 82 and the briquette B, respectively, progresses. Once the quantity of the frictional wear increases to a value in excess of a limit, the phenomenon similar to that discussed above occurs, resulting in difficulty in completing the compression of the grinding sludge.
(2) Plug-like Double Cylinder Type (FIG. 10)
At the time of compression and ejection of the briquette B, the briquette B is pushed by the pressure applying main cylinder 95 while an outer peripheral surface of the briquette B is firmly urged against an inner peripheral surface of the sleeve 91. For this reason, the inner peripheral surface of the sleeve 91 is susceptible to frictional wear and, when in the last, a gap between an outer peripheral surface of the sub-piston 92 and the inner peripheral surface of the sleeve 91 increases to a size in excess of a limit, either the grinding sludge will blow off during the compressing operation, or the sludge will solidify within the gap between respective outer peripheral surfaces of the pistons 92 and 93 and the inner peripheral surface of the sleeve to such an extent that the coolant cannot be drained satisfactorily, resulting in difficulty in completing the compression of the grinding sludge.